1. The Field of the Invention
This invention relates to an assembly for etching semiconductor surfaces by the combined action of agents which oxidize the semiconductor material and which dissolve the oxidation product, and also to an apparatus for carrying out the process.
2. Description of the Prior Art
It is known that surfaces of elementary semiconductors such as silicon or germanium are treated by means of etching solutions in which an oxidizing agent and an agent which dissolves the oxidation product produced in the process always act together. Examples of such etching solutions are mixtures containing, for example, nitric acid, dichromate or permanganate as oxidizing agents, and hydrofluoric acid as the agent which ultimately dissolves the oxidation product, for example, silicon or germanium oxide. These known etching solutions frequently also contain diluents such as water, acetic acid, glycerine, phosphoric acid or according to Austrian Patent Specification No. 377,868, sulfuric acid. In this patent, numerous further common etching solutions are also discussed.
However, with these known etching solutions, the action decreases to an increasingly considerable extent as the duration of use increases. Thus, these solutions have to be checked frequently to even guarantee reproducible results of the etching process. This results, on the one hand, in a considerable requirement for unused starting materials to replace used components, and on the other hand, these quantities of used etching mixtures have to be disposed of and this may cause environmental pollution.